The present invention is concerned with plastic compositions which contain a tetracarboxylic acid tetraester-plasticizer. Said plasticizer is a benzhydrol-tetracarboxylic acid tetraester in which the esterifying alcohol components are alkanols, alkenols or alkinols and said alcohol components comprise 4-24 carbon atoms.
Said tetracarboxylic acid tetraester is rather firmly anchored in the matrix of plastic material so that even after extended storage periods no migration of the plasticizer in the matrix of the plastic material occurs. Due to the firm anchoring of the plasticizer in the matrix of the plastic material said plasticizer also does not migrate into solid materials or liquids which are kept in contact with the inventive plastic compositions.
If the inventive plastic compositions comprise in addition to the plasticizer at least one further component having a not too low molecular weight, e.g. a molecular weight of about 100 or higher, then also said component is anchored in the matrix of the plastic material through the benzhydrol-tetracarboxylic acid tetraester. Said further component can e.g. be an ion sensitive component and corresponding ion sensitive parts accordingly have a very long life period. Contrary to this, the benzophenone tetracarboxylic acid tetraester of the inventive plastic compositions do not inhibit the migration of small ions like cations of alkaline earth metals or alkali metals or the anions of halides or carbonate anions. so that corresponding ion selective parts are well suited for the determination of the concentration of the corresponding anions or cations in liquid media.
Inventive plastic materials which contain high quantities of the tetracarboxylic acid tetraester-plasticizer, like 15-90 parts by weight of said plasticizer per 10 parts by weight of the plastic components, have high elasticity and high adhesive characteristics.